With increasing development of science and technology, charging systems are widely used in many fields. For example, charging systems are used for charging electric vehicles.
Generally, the charging system comprises a bus capacitor. When the charging system starts up to receive the input AC power, a large transient current is generated to charge the bus capacitor. The large transient current is also referred as an inrush current. The inrush current may damage the internal electronic components of the charging system.
For solving the above drawbacks, the conventional charging system is further equipped with an AC relay and a current-limiting resistor. The AC relay and the current-limiting resistor are connected to an input terminal of the charging system and connected with each other in parallel. Before the charging system starts up to receive the input AC power, the AC relay is turned off. Consequently, the current-limiting resistor limits the peak value of the current to decrease the inrush current. After the charging system finishing starting up, the AC relay is turned on. Consequently, the charging system receives the input AC power through the AC relay.
Since the charging system is additionally equipped with the AC relay and the current-limiting resistor, the cost of the charging system is increased. Moreover, since the AC relay has poor reliability and short life, the charging system is readily damaged. In addition, the AC relay with high power has not been introduced into the market. When the charging system is applied at a high power situation, the AC relay and the current-limiting resistor cannot be used.
Therefore, there is a need of providing a charging system and a method in order to overcome the above drawbacks.